The present invention relates to an apparatus for measuring tension in a linear material and more particularly relates to an apparatus for measuring tension in a traveling linear material and which may include means responsive to such measured tension for keeping a substantially constant tension on the material.
It is possible to arrange apparatus for measuring tension in a linear material into two categories, direct and inferential. Direct tension measuring apparatus directly measures tensile force in a linear material. Inferential measuring apparatus infers tension in a linear material from properties and relationships of the material that can be related to the tension in a material.
A tension measuring apparatus is particularly useful in making glass fibers especially in a process for forming a continuous glass filament where such filaments are attenuated from streams of molten glass provided from a supply of molten glass. Suitable means gathers the filaments into a strand which are collected by suitable winding or advancing means at speeds from several thousand to ten thousand or more feet per minute. Variations in linear speed of the advancing strand or filaments changes the tensile force in the material, such variations affecting the diameter of the filaments themselves as they are attenuated from streams of molten glass. Tension measuring devices are used to measure the tension in a material and responsive to that measured tensile force modulate process conditions to keep the tensile force in the advancing linear material such as glass strands substantially constant so more uniform filament diameters are produced.
An improvement in tension measuring devices is shown in U.S. Pat. No. 3,526,130 issued Sept. 1, 1970, and assigned to the common assignee of this application.
In that device, the tensile force in a linearly extended material is measured as a function of the strain induced by the linear material. More particularly, the traveling flexible material, such as glass fiber, is bent a predetermined angle to induce a rotational force or moment about a cantilevered arm which is supported at one end. According to the relationship shown in the U.S. Pat. No. 3,526,130, the transducers are placed at a predetermined location on the arm such that the strain induced in the transducer by the force of a material as it bends against the apparatus is directly related to the tensile force in the material.
However, in accordance with the relationship shown in that prior art patent, the path of the material must be toward and intersect with that same location on the cantilevered arm where the transducers are mounted. For practical reasons, a second turn is imparted to the material after the bend so a colliding intersection with the transducers is avoided. The path of the material is then diverted around the transducers to the take up reel or winder.